1. Field of the Invention
This invention relates to a process for producing purified hydrochloric acid, and more particularly it relates to a process for producing concentrated hydrochloric acid having little impurities from hydrogen chloride gas generated by reacting an alkali chloride with sulfuric acid.
2. Description of the Prior Art
A process of reacting an alkali chloride with sulfuric acid to generate hydrogen chloride which is then caused to be absorbed into water to produce hydrochloric acid (which process will be hereinafter referred to as "conversion process"), is a technique being reevaluated in these days when energy-savings are desired. This is the case since such a large amount of electric power is not consumed as in the case of an electrolysis process of alkali chlorides; hydrogen chloride, not chlorine, can be directly obtained; and at the same time, useful alkali sulfates can be obtained.
However, in the case of hydrochloric acid obtained according to the conversion process wherein an alkali chloride and sulfuric acid are present as raw materials, impurities contained therein, e.g., an alkali sulfate formed at the reaction time of the conversion process, etc., mix in the hydrogen chloride generated in the form of dust or mist. Thus, hydrochloric acid produced by absorption of such hydrogen chloride in water is more impure than hydrochloric acid from hydrogen chloride obtained by reacting chlorine with hydrogen, and purification by redistillation or reabsorption has been required even for chemical industry uses.
In view of such a situation with hydrochloric acid produced according to the conversion process (which will be hereinafter referred to as "conversion process-hydrochloric acid"), the present inventors have studied a purification process wherein impurities present at the time of the conversion reaction do not mix in the conversion process-hydrochloric acid, and as a result have found that dust of potassium sulfate, etc. and mist of sulfuric acid (which will often be hereinafter referred to as "sulfuric acid mist, etc.") can be fully removed by washing the hydrogen chloride generated by reacting an alkali chloride with sulfuric acid, with hydrochloric acid having a saturation concentration.
As apparent from the foregoing description, an object of the present invention is to provide a process for producing purified, conversion process-hydrochloric acid without the need of any particular purification step such as redistillation or reabsorption.
Another object of the present invention is to provide purified hydrochloric acid produced according to the above process.